Pump and/or rotative compressor with prismatic pistons



March 19, 1957 MENON 2,785,851

PUMP AND OR ROTATIVE COMPRESSOR WITH PRISMATIC PISTONS Filed May 27, 1952 ATTORNEY United States Patent() PUMP AND/R ROTATIVE COMPRESSOR WITH PRISMATIC PISTONS Luigi Menon, Genoa-Recco Mulinetti, Italy, assignor to U. B. I. S. p. A. Utilizzo Brevetti Industriaii, Genoa, Italy Application May 27, 1952, Serial No. 290,258

Claims priority, application Italy June 11, 1951 7 Claims. (Cl. 230-153) The present invention is concerned with a mechanical device which may be used as a pump or as a rotary compressor, the device having prismatic pistons and, as a result of its structural details and its characteristic construction, has important advantages in operation.

ln the following portions of this specification the device in question will, in order to simplify its description, be designated as a compressor, but it will be understood that it may also be designated as a pump The compressor according to the present invention is of a type which has a cylindrical rotor concentrically disposed in a cylindrical housing, the rotor being provided with radial slots receiving prismatic pistons or plungers which slide in the slots and are the active elements of the compressor.

The compressor is characterized by the fact that the internal surface of the stator is defined by two portions, one portion corresponding to the exterior surface of the rotor and having substantially the radius of the rotor which rotates against it tightly, while the other portion has a greater radius and has its central axis displaced with respect to the axis of the rotor in order to provide for the radial movement of the pistons. The inlet and outlet mouths of the compressor are disposed at the beginning and at the end of the portion having the cylindrical surface of greater radius.

The compressor is further characterized by the fact that adjacent the mouth of the suction inlet into the internal chamber of the stator there is disposed a suction chamber which extends from the beginning of the surface of greater radius of the internal chamber of the stator in the direction of movement of the rotor, whereas adjacent the mouth of the delivery outlet in the internal chamber of the stator there is disposed a delivery chamber which extends from the end of the surface of greater radius of the internal chamber of the stator in a direction opposite to that of movement of the rotor. The extent of the suction and delivery chambers is such that, when a piston has left, in the course of movement of the rotor, the edge of the suction chamben'the preceding piston will put the delivery chamber in communication with the pressure chamber of the compressor.

The compressor according to the present invention is further characterized by the fact that on each side of the rotor there is an element provided with a groove or channel which is concentric with respect to the internal surface of the housing, and in this groove or channel there is seated, on each side of the rotor and for each prismatic plunger or piston, a slipper, the slippers and the prismatic pistons being pivotally connected or articulated. The compressor according to the invention is further characterized by -the fact that the slots or recesses in which the pistons slide communicate with each other on radially opposite sides of the rotor.

In the particular embodiment in which the number of prismatic pistons or plungers is even, viz. when there are oppositely-disposed plungers, the compressor is charac- -terized by the presence of elastic means disposed in radi- Patented Mar. 19, 1957 fiice ally extending bores in the rotor, the elastic means constantly pushing the two oppositely-disposed plungers radially outwardly.

The compressor according to the present invention, particularly when it is designed to function as a compressor for gaseous material, is characterized by the fact that the shaft of the eccentric rotor which carries the radial grooves or seats for the prismatic plungers, is axially bored from one end which communicates with a lubrication chamber in which means are disposed to permit the open end of the bore to communicate with the portion of the lubrication chamber in which the oil gathers. At the same time communication is provided between the compressors delivery conduit and said chamber for the oil, so that the oil is continually urged between all movable parts of the compressor so as to form a film of oil between them which also acts as a sealing means.

The compressor according to the invention is further characterized by an element in the delivery conduit, through which the pumped uid is forced along a tortuous path, by means of which the uid is freed from almost all the oil particles carried by it.

The compressor is also characterized by lthe fact that `it has an abutting wall inclined in the moving direction of the pumped uid, the fluid being thus forced to strike against its lower surface and to slide along it before ilowing towards the outlet and there is thus obtained a second separation of oil particles from the fluid. The ends of a space which exists under said Wall communicate on one side with the oil container and on the other side, by reason Vof a perforation in said wall with a sealing valve.

In the accompanying drawing there is shown solely by way of example a preferred embodiment of the invention. In the drawings,

Fig. l is an axial diametrical sectional view of the pump or compressor of the invention, taken along the line I-I of Fig. 2;

Fig. 2 is a sectional view taken along a line perpendicular to the axis of rotation of the rotor; and

Fig. 3 is a sectional View along the line III- III of Fig. 2.

Referring to the drawings, the oblique ball bearing 2 is mounted in plate 1 and a face piece 3 of tempered steel Which has an annular groove 26 of square or rectangular cross-section which is eccentric with respect to the axis of rotation of shaft 27 and of rotor 28. The compressor body 4 has an annular chamber with two different radii. One surface of radius 3@ is concentric with the axis of rotation and closely follows the radius of rotor 28. The other surface substantially of radius 31 is eccentric with respect to the axis of rotation of the rotor. The arcs drawn by the two radii meet in the points 32 and 33 of the compressor body 4, which correspond to the nearest portions of lthe suction orice 34 and of the delivery orifice 35.

Communicating with said openings, there are provided a suction chamber 58 and a delivery chamber 59 respectively, the extent of said chambers being such that, when a prismatic piston 17 has left, during its movement, the edge of the suction chamber 58, the prismatic piston 17 which precedes it in movement, puts the delivery charnber 59 of the compressor in communication with the delivery conduit of the compressor.

A device 5 is mounted in the delivery orifice by means of nut 6, device 5 acting as an oil separator and silencer and communicating with the interior of a hood 7 through a conduit 36'. Separator 5 has openings 56 and 57 :for

ow of fluid through it. The hood 7 has seated in it a second face piece 8 of tempered steel which, like face piece 3, is provided with an annular groove 37 of square or rectangular cross-section which is eccentric with respect to Visvalsoforrned.inhood 7, through theconduit. In theV pressure conduit 40 there isv mounted a' sealingV valve 4l contained in a body 42, with a valve bodyr43 and a connection piece 44. The container 39 is closely sealed for pressure by cover lzrwhich has a plug 13 providedwith a rod 45 for measurement ofthe oil level.

The rotor V2S is provided with the bushings 15 and counter-pushers 16 for regulating the-position of the rotor. The rotor 28 has radial recesses or cuts 46 in which are located the prisrnatic plungers 17 on which slippers 18 are secured. The slippersV are each connected to a plunger 17 by a pin 19, andiare slidably received in the annular grooves 2.6 and 37; Between thecounterposed plungers 17 and extending through the radial. bores 47v formedin rotor 28 are resilient buffers for Ycorrecting any clearances which mayrdevelop in the operation of the device. The buffers are made of a sleevefi, a spring 49,-and a small plunger 50; t

Along the axis of shaft 27 there is formed a bore 51, which communicates with all of the radial ,bores 47 in which the buffers 48-50 are locat1ed andat.. its end com;

municates with the oil container 39 by wayof the small bearingmember 21 which is disposed inside the container 39. The small bearing member has a seat 52 in which is mounted a gasket which seals on an abutment 53 at the end of shaft 27 of rotor 28. The axialy bore 51 cornmunicates with conduit 54 of the small bearingmember 21, conduit V54 opening towards the bottom of container 39. The outlet end of shaft 27 extends through a cover 23 which cooperates with an annular gasket extension 24 to eieot the desired pressure sealing4 of the shaft.

The above-described device operates in the followingY manner. When a motor (not shown) is coupled with. the

rotor 28 the rotor is driven in thev direction of. arrow S5 A and carries with it the prismatic plungers 17 seated in radial cuts 46 of therotor. Because the prismatic plungers are connected by pins 19 (on whichv they arev free to oscillate) to the slippers 18 which run in the annular grooves 26 and 37 positioned eccentrically.y with respect to the axis of rotation of the rotor, butconcentric to the axis on which the center of the radius 21 of the cornpressor body 4 is placed, the plungers are kept in continuous contact with the internal surface of the compressor body along the portion of the body when pressure sealing is necessary and out of contact with it when. such sealthough they were connected to a continuousV crank. However, they have no rigid connection with the shaft of the rotor and they therefore do notcause vibrations due to alternately moving masses. Furthermore, because the plungers rotate with respect to an axis that is concentric to the axis of the annular grooves in the face pieces, they are-not submitted to. reciprocatingmotions and therefore are not subject to radial acce'lerations or decelerations.

Whatever the position taken by the.l rotor may be, the

center of gravity of all static parts and all dynamic parts always passes through the axis of the rotor and the machine is therefore always equilibrated.

The air or gas sucked in through the suction orifice 34 ispressed into-the delivery orifice 44, passes through the separator 5, thel separator 10, and the sealing valve 43, and iiowsv to a reservoir or to the user.

During operation, the pressed air or gas operates on the surface of the oil which is. in the container`39 and causes -it to move upwardly from the bottom of the latter along the: conduit 54 ofthe smalllbearing member 21 and along the-.bore 51. formedv axially in the shaft 27, thus lubricating the buifers48-5 aswell as, byreason of the presence'of the; radial bores47 containing the buffers, the external-surfacesrofthe prismatic plungers 17, which lie in the radial recesses in the rotor 2S, and the surfaces mg is no longer required. The plungersthus operate` asY ofthe slippers '18 which are seated in the annular grooves 26 andS'Z. Theoil, whichis, in this mannenspreadon the sides of the moving elements increases their sealing because, due to its viscosity it acts as a hydraulic sealing element, taking the place of expansion packing rings with the advantage that. it .preserves the parts from wear. The surplus oil that is carried into the delivery or-iiice is separated from the air and the gas by thei'a'foresaid separators 5 and 10,. due to the tortuous path defined bythe openings 56 and 57 and to the lower surface of the inclined separator/wall 10, and i's led back into lubricating chamber '39 ythrough conduit 38 withoutzleaving th-e compressor. Y

' Although for purposes of illustration the present invention has been described in termsof theV embodiment shown by way ofy example in the accompanying drawing, many changes and-modifications may be made in this embodiment. Thus, for instance, an air or water cooler for the compressor may be provided'or the compressor maybe connected with others in a plurality of phases. VThese and other additions and variations must-be-consideredas. comprisedv within the scope and spirit of the invention asi first arcuate portion that is concentric with the axis of rotation of said rotor hasta radius substantially equal to said rotor whereby to receive the surface ofsaid rotor with a close iit to provide fluid-tight sliding Contact between the rotor and the cylindrical surface of the first arcuate portion, and -a second arcuate portion of'substantially cylindrical outline having its center spaced from: Y

said axis of rotation in adirection away from said rst arcuate portion Vand having a radius greater than that of.

the first arcuate portionan inlet opening .at one end of the cylindrical surface of said first arcuate portion and an:

outlet opening at the, other end of the cylindrical surface of said first arcuate portion, said openings communicating. with said second arcuate portion, the distance between said openings along said cylindricalv surface of said first arcuate portion being less than Vorisrnatic pistonsV slidably disposed in said radial slots, said pistonsrbeing movable radially from a position interiorly of said rotor to a position in which said pistons extend at least partly from said rotor, the walls of said chamber perpendicular to said axis of rotationY being formed withr'cylindrical grooves disposed eccentrically with respect to said axis of rotation, arcuate guides slidably mounted for circular movement in said groove, and means pivotally connecting a guide to each of said pistons whereby the radialmovements of said pistons are controlled by the position of said guides in said grooves, said grooves being shaped to move the free end of each of said pistons into engagement with said secondarcuate Vportion between said inlet openf ing and said outletV opening, and said end of each piston being chamfered in a direction awayfrom the direction of rotation of said rotor, whereby only the leading edge of each piston is in engagement with the surface of said second arcuate portion upon rotation of the rotor, the remainder of the end surface of said pistons being spaced from said second arcuate portion surface.

2. A rotary pump as defined in claim l, wherein there is an even number of pistons and wherein said rotor is formed with radial perforations between opposite slotsv in the rotor, and spring plungers are disposed in said perforations to `act on opposite pistonsrto urge them radially outwardly from one another.

3. A rotary pump according to claim l, in wh'ichsaid rotor is provided with passageways interconnecting said slots with one another to permit iiow of fluid from one slot tov another.

4. A rotary pump according to claim l, in which a suction chamber communicating with said inlet opening atends from the beginning of the portion of the pump chamber surface having greater radius in the direction of movement of said pistons and a delivery chamber communicating with said outlet opening extends from the end portion of said surface having greater radius in a direction opposite to the direction of movement of said pistons, the extent of said suction and delivery chambers being such that when a piston has left the edge of the suction chamber, the preceding piston puts said delivery chamber into communication with said pump chamber.

5. ln a rotary pump, a pump chamber having bores in opposite end walls, a cylindrical shaft rotatably supported in said bores, a rotor on said shaft in said chamber, said rotor being provided with a plurality of axially-extending radial slots, the inner surface of the pump chamber cornnrising a cylindrical first arcuate portion that is concentric with the axis of rotation of said rotor and has a radius substantially equal to said rotor whereby to receive the surf ^e of said rotor with a close t to provide fluidght ing contact between the rotor and the cylindrical surface or" the iirst arcuate portion, and a second arcuate portion or" substantially cylindrical outline having its center spaced from said axis of rotation in a direction away from said rst arcuate portion and having a radius greater that of the rst arcuate portion, an inlet opening at one end of the cylindrical surface of said t'irst arcuate portion and an outlet opening at the other end of the cylindrical surface oi said rst arcuate portion, said openings communicating with said second arcuate portion, the distance bet veen said openings along said cylindrical surface ot first arcuate portion being less than 180, g isniatic pistons slidably disposed in said radial slots, said pistons being movable radially from a position interiorly of said rotor to a position in which said pistons extend at least partly from Said rotor, the walls of said chamber perpendicular to said axis of rotation being formed with cylindrical grooves disposed eccentrically with respect to said axis of rotation, arcuate guides slidably mounted for circular movement in said groove, and means pivotally connecting a guide to each of said pistons whereby the radial movements of said pistons are controlled by the position of said guides in said grooves, said grooves being shaped to move the free end of each of said pistons into engagement with said second arcuate portion between said inlet opening and said outlet opening, and said end of each piston being chamfered in a direction away from the direction of rotation of said rotor, whereby only the leading edge or" each piston is in engagement with the surface of said second arcuate portion upon rotation of the rotor, the remainder of the end surface of said pistons being spaced from said second arcuate portion surface, said cylindrical shaft having an axial bore cornmunicating with the interior of said chamber, a lubrication chamber communicating with an outer end of said bore and adapted to contain a lubricant and a passageway connecting said lubrication chamber to said outlet opening to apply pressure to said lubricant in said lubrication chamber and to return to said lubrication chamber any lubricant discharged through said outlet openinv,

6. A rotary pump according to claim 5, in which a discharge passageway is connected with said outlet opening, said passageway providing a tortuous path of ow for liuid discharged from said chamber to separate from said fluid any entrained lubricant particles.

7. A rotary pump according to claim 5, in which a lubricant separation chamber is connected with said outlet opening, aid lubricant separation chamber containing an inclined wall against the lower surface of which fluid discharged frorn said pump chamber impinges, communication being provided from said separation chamber for the return or" lubricant to said lubrication chamber.

References Cited in the le of this patent UNETED STATES PATENTS 118,993 Wentworth Sept. l2, 1871 465,907 Whipple Dec. 29, 1891 1,686,272 Goodridge Oct. 2, 1928 2,260,888 Davis Oct. 28, 1941 2,305,317 Nicltell Dec. 15, 1942 A323,802 ick et al July 6, 1943 2,367,326 Beckman Jan. 16, 1945 2,696,715 Martin Aug. 12, 1952 FOREIGN PATENTS 129 italy of 1875 25,035 Great Britain of 1912 286,240 Great Brit-ain 1929 340,929 France May 27, 1904 672,058 France Sept. 14, 1929 

